The present invention relates to semiconductor devices and semiconductor device assemblies and in particular to a semiconductor device and a semiconductor device assembly incorporating a magnetoresistive element.
As semiconductor devices such as semiconductor integrated circuits for storage, DRAMs (Dynamic Random Access Memories) and SRAMs (Static Random Access Memories) have been conventionally in wide use. MRAMs (Magnetic Random Access Memories) are devices that store information by magnetism and are superior to other memory technologies in high-speed operation, rewriting resistance, nonvolatility, and the like.
The MRAM incorporates a magnetoresistive element designated as MTJ (Magnetic Tunnel Junction) element utilizing the TMR (Tunneling Magnetoresistive) effect and stores information by the magnetization state of the magnetoresistive element. The magnetoresistive elements are arranged in areas where digit lines extended, for example, in one direction and bit lines extended in the direction substantially orthogonal thereto intersect with each other and are formed in an array configuration. In each magnetoresistive element, two magnetic layers are laminated with a tunnel insulating film in between. Each magnetoresistive element includes a layer the direction of magnetization of which is varied by a magnetic field generated by currents passed through a digit line and a bit line. The magnetoresistive element stores this direction of magnetization as information. The electrical resistance of the magnetoresistive element is varied according to the magnetization direction of this layer. The information stored in the magnetoresistive element is detected by detecting change in the current passed through the magnetoresistive element by this variation in electrical resistance.
In general, a cladding layer including a high permeability film comprised of a thin film formed of a material high in magnetic permeability is arranged over the side surfaces and upper surfaces of wirings such as bit lines. This is intended to intensively supply a magnetoresistive element with a magnetic field generated by currents passed through a bit line and the like in the above-mentioned semiconductor device. It is further intended to shield a magnetic field supplied to that magnetoresistive element against magnetic fields generated by currents passed through bit lines and the like other than the desired bit line.
For example, in the semiconductor device described in Japanese Unexamined Patent Publication No. 2009-38221 (Patent Document 1), a high permeability film is formed above the bit line of each magnetic memory element with an insulating film in between. The high permeability film arranged above a bit line as mentioned above has a role to block off magnetic fields (external magnetic fields) generated by currents passed through bit lines other than the relevant bit line so that the following is implemented: problems that arise when the magnetoresistive element arranged under the bit line is influenced by the external magnetic fields are suppressed.
For example, in the semiconductor device described in US 2004/0032010A1 (Patent Document 2), a shielding layer (equivalent to a high permeability film) formed of amorphous soft magnetic material is arranged above an MRAM device. Layers formed of amorphous soft magnetic material as mentioned above have a role to suppress reduction in magnetic permeability due to eddy current or ferromagnetic resonance and suppress degradation in the functionality of MRAM devices.
[Patent Document 1]
    Japanese Unexamined Patent Publication No. 2009-38221[Patent Document 2]    US 2004/0032010A1